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Which flat roof system is best?

Let’s cut right to the chase. “Which flat roof system is best?” really isn’t the right question. Instead, you should ask “which flat roof system is appropriate?” You see, the ‘best‘ flat roofing system for Joe’s Computers might not be appropriate for Diane’s Day Diner is she’s looking for the ‘best flat roof system’. If Joe is looking for ‘the best flat roof’ for his computer repair building, that’s probably TPO or EPDM. The ‘best flat roof’ for Diane’s Day Diner is PVC, since it’s resistant to cooking grease, oil, and fire. PVC is overkill for Joe’s building. It’s inappropriate. It would be a waste of money for Joe. But PVC is the best for Diane.

The most appropriate flat roofing system really comes down to 2 questions:

Will there be cooking in the building or not? If there will be, go with PVC* since it’s resistant to fire, fat, grease, and oil.
*Depending upon the amount of cooking, you might be able to get away with something other than PVC. Contact us for our recommendation.

If there won’t be any cooking in the building, is money a concern? If so, go with EPDM or Modified Bitumen as these are your least expensive flat roofing systems yet still great products. If money isn’t an issue, choose TPO since it’s strong yet less expensive then PVC.

Also see related article Which roofing material is right for you.

Want to learn more? Keep reading.

Did you know that flat roofs aren’t just for commercial buildings? Actually, we’ve installed flat roofing systems onto residential garages, home additions, and more.

What is a flat roof? What qualifies as a ‘flat’ roof?

A flat roof is a roof that, well, looks flat. It’s not really flat, however. It’s a roof whose pitch, or angle, is less than 2/12, or 9.5º. (2/12 means for every 12″ of horizontal length, the roof rises 2″ in height.)

side view of a commercial building with a flat roof that has a 2 degree pitch angle

side view of a commercial building with a flat roof that has a 2 degree pitch angle

What are your flat roof options?

Although there are several flat roof systems available today, in this article, we’re only going to cover the systems we offer. Those are PVC, TPO, EPDM, and Modified Bitumen.


For most businesses, the cost of a commercial roof is the first consideration; which commercial roofing system is the least expensive, not only to purchase, but to install, maintain, and repair. Cost should not be your only consideration, however…


Really, the first question on everyone’s mind when choosing a flat roofing system should be whether there will be a lot of cooking in the building. If there will be, because you own a restaurant or a hospital, you should use PVC because it is resistant to fats and greases and fire. If you just focused on cost and put an EPDM roof on your restaurant, the grease that gets sucked-up through your ventilation will be deposited onto your roof and that EPDM roof will breakdown quickly, costing you more money in the long run.

flat pvc roof of LuLu Asian Bistro

flat pvc roof of LuLu Asian Bistro

Foot Traffic

Foot traffic used to be something to consider. Today, however, any flat roofing system can accommodate a walkway. That said, PVC is considered the preferred roofing material since it is the strongest.


If saving money on energy bills is important to you, then you might want a white or highly reflective roofing system. White reflects heat, therefore keeping the inside of your building ‘cooler’. Just like foot traffic, any of the flat roofing systems we talk about here can be ‘cool’. For example, EPDM natively comes as black, but a white layer can be added to make it ‘cool’. PVC and TPO, however, natively come in white, so no additional layer is required.

Wait! What about shingles, tile, and metal?

Asphalt shingles, tile, and metal aren’t considered “flat” roofing systems. These roofing systems require a roof pitch greater than 2/12 or 9.5º. If these non-flat roof materials are installed onto a roof that’s less than 2/12, you run the risk of water leaks because rain water is shed more slowly on these materials if used on a ‘flat’ roof.


Remember, money shouldn’t be your only consideration when choosing a flat roofing system. Also consider what’s appropriate for your application. Sometimes the system that costs more initially, might cost less in the long run because it lasts longer and requires less maintenance and repairs. Keep in mind that the best flat roof for one person or building might not be the best for you. Most commercial buildings that aren’t restaurants have TPO or EPDM. Restaurants should only use PVC. If in doubt, contact us for our recommendation.